Riihimaen did make clear glass items.

I've got one signed Tamara Aladin (shown on another thread) for Riihimaen, and another 'Finncrystal' (which was their export label) Riihimaen vase.
From left to right: 'Finncrystal' (Riihimaen export label), Tamara Aladin in the middle for Riihimaen, & a Krosno vase on the right.

The 'Finncrystal' vase on the left is good quality, but has an odd straw colouring. I don't really like these clear vases, and I think generally they're less popular than their cheerfully coloured stablemates.
Fact about Finncrystal taken from: 'Smoke & Ice'